The blast tore through the ranks of the parade, its metal-packed heart shattering windows and ripping through bodies in a wide arch of mayhem that littered lower Market Street. It knocked policemen off their horses and even threw a man's hat and a severed ear atop a nearby building.

It had come from an exploding black suitcase, set down beside a wall of the Ferry Exchange Saloon at Steuart Street, which cut a gaping hole through the bar's wall.

“The air was filled with death-dealing metal,” Charles Frye, who was knocked to the ground standing 50 feet away, told The San Francisco Examiner about The City's deadliest single criminal act: the 1916 Preparedness Day bombing.

Ten died from the blast and 40 were wounded. No other single act of violence — not the 1934 general strike, the Zebra killings in the early 1970s or the Golden Dragon massacre — would match it in sheer body count. While the aftermath would have lasting impacts on those hunted and eventually framed for the crime, The City as a whole has not remembered this event as much as one might suspect.

Minutes before the July 22, 1916 explosion — called an anarchist act of terror almost as soon as it went off — about 50,000 marched from the Ferry Building up Market Street in a parade put on by the Chamber of Commerce and other conservatives to press for American involvement in World War I. Some have called it the largest parade The City has ever seen.

Besides the soldiers and veterans, the parade looked innocent enough — it included women dressed in white with American flags over their shoulders and even a boy in a suit made of stars and stripes.

But the march had its opponents in progressive and radical circles. William Jennings Bryant, the progressive firebrand, called the march an effort by business interests to make money off the war. Radicals opposed it and the war, because they saw WWI as a fight between capitalists and emperors, not working men.

But the only sign that a bomb might disrupt the event came in the form of an ominous anonymous letter sent to police before the procession, warning of violent action.

THE REACTION

The Examiner's July 23 edition, and the following day's, listed the names of the dead and retold individuals' stories from the day, but most of all it called for blood. Articles appeared calling for ridding The City of “anarchists.” As each suspect was arrested, their faces appeared on the front cover. One was simply called a “dynamiter,” another an “agitator.” Much of the rest of the coverage was laden with similar language: The bombing was an “outrage” and a “tragedy.”

Off the pages, more than 100 special police were called in to aid the search, and the business community and the Board of Supervisors promptly raised a reward that swelled to $17,000.

“San Francisco must now prove to the world that it is ready…to root out forever the criminal element as well as the responsible agitators, who, preaching class hatred, have caused criminal minds to commit this outrage,” said the head of The City's Civic League of Improvement Clubs.

The hunt cast a wide net and didn't last long. Anyone and everyone linked to radical politics or labor unionism was rounded up as a possible suspect. A Finnish sailor was arrested for reportedly saying, “Well, that is what comes of preparedness.” Another man, a member of the Industrial Workers of the World, was arrested in Fresno for voicing similar sentiments.

A group of suspects started being arrested within days of the bombing and included mostly labor activists. Thomas Mooney, who had faced charges for allegedly bombing a PG&E power line in San Bruno in 1914, was arrested with his wife, Rena Mooney, after they surrendered. Warren Billings, another labor activist, was also arrested, along with two others.

It was Mooney and Billings who finally faced trial. Billings was found guilty and sentenced to life in prison in 1916. Mooney was convicted of murder in 1917 and sentenced to death. But within a year, Mooney's death sentence was reduced to life imprisonment after President Woodrow Wilson asked the governor to commute the sentence.

By that time evidence began coming out that proved the men had been convicted through false witnesses and perjury. Still, it wasn't enough to free the men, whose cause was kept alive for two decades.

In one film shot for Mooney's defense from 1933, he tells the camera, “I have suffered 17 years of a cruel and unjust imprisonment for the reason that I was an active, militant, aggressive trade unionist.”

In 1939, the pair were released from prisoner when Gov. Culbert Olson pardoned Mooney and commuted Billings' sentence. The men had served more than two decades in prison.

Mooney, whose imprisonment along with Billings became a cause celebre, walked at the head of a pro-union parade up Market Street in January 1939. He died several years later.